Carburetor Drilled Return Pressure Balancing Modification GPR, XLT, GP, SUV, etc.

[Adam]

I haven’t seen a check valve fail with this modification, I believe it takes the pressure spike off the check valve and prolongs their life . Diaphragms fail before the check valves and fuel pressure drops . As you said rebuild every 3 yrs to keep everything reliable. I have just pulled apart my carbs after I noticed the pressure drop on the gauge I have installed. Diaphragm is leaking pulse pressure and not keeping up with fuel demand of my Triple piped GP1200R , better safe than sorry.

[kartracer]

So how do you check fuel pressure on carbs. without this mod. ????

[Cutlass]

So how do you check fuel pressure on carbs. without this mod. ????

You can't.

[steelmesh]

95 main jets are hard to come by locally (M5 thread, 6mm round head). I have the old 95 pilot jets, but those are 4mm threads so won't screw into that last nipple. Here is one alternative to using the 95 pilot jet for the return using vacuum line couplers. I soaked one in gas last year and nothing happened fyi.

1/4" and 1/8" nipples, drill out the 1/4" to size so the 1/8" friction fits, tap the 1/8" with M4 thread and finally trim them down to insert into the hose:









And I did tap the last nipple so confirm it works. I only have a M5x0.8 tap, so the M5x0.7 jet will go half-way and start "self locking itself" which might be a good thing but could be a disaster to service/clean cause you might not be able to remove it:

[jeflyer]

I bought a 2001 model XR1800 ten years ago and did all the mods. It was a DOG due to unsolvable carb issues.Then the right engine blew for the third time. Everyone advised me to ÔÇ£dump that boat!ÔÇØ

But it I know it inside out and love the concepts in the XR1800, it's sleek lines, twin jets, etc, etc. Plus, it fits inside my home garage.

9 years of searching for answers and trying everything to remedy that lousy carb hesitation! One day last autumn I stumbled upon the 2012 thread with OsadeBill writing out his carb mod Recipe, just before he died. That had to be it! So, I this time ordered a new rebuilt engine from SBT and chipped away at the project through the winter months in my house garage. I didn't know what many of the terms meant in the Recipe, but others on the forum described them, with photos. I went for it and drilled out the returns, added the 95 restrictor, made a pop off pressure gauge and adjusted the jet screws, replaced the oil and fuel lines, bought and learned to use twist wire pliers to clamp all those hose connections. I looked forward to moments when I could go out chip away at the project. Sadly, one day in January it was all completed, nor more project.

I then researched how to break in the new jet ski engine. Made up a temporary separate fuel line for that engine to use breaking premix. Took it to Lake Samish and broke it in. All this spring and summer I've cruised around the San Juan Islands and fishes for salmon in Baker Lake. What a different boat!!! Hole shot every time, never stalls, bogs, or quits ever. Hardly see any smoke anymore either. I've added SmartTabs that made a huge difference, installed blue LED lighting throughout, plus 4 white LED interior lights, LED bow light, a detachable Scotty down-rigger, detachable transom mounted Minnkota 24V trolling motor, etc. Finally have a great XR1800 and all of you to thank! -JE

[woodsrider40]

I know this is an old post. Is the 98 XL 1200 same as the gp ? Is the N/S 1.2 or change, any jetting needs done and last what pop off pressure.

[greenwoodthomas]

I have the same question regarding the 1998 model xl1200

[Cutlass]

Yes, the 98 XL1200 has the same engine as the GP1200 and the mod would be the same.

[Jonesyfxr]

We are amidst doing the dual feed mod, fuel clunks and extended pickups. According to Osidebill, the GP1200R doesn't need a restrictor on the return unless you drill the carb bodies... so we are foregoing the return line jet at this time.

After having the ski out over Memorial Weekend, I noticed 2 stroke oil in the bilge under the carbs...this encouraged us to remove the pipe and investigate. I found the middle cylinder oil supply line barely on the nipple. So we also went to pre-mix and an oil pump block off plate.

While we are at it, we are installing the Island Racing Holeshot kit (Jetworks mod). We are also installing a bilge pump, using the supplied RIVA template off this form. I made the bracket out of a 1/8" sheet of ABS plastic. It was a clean install for sure!!

The one question I have....
What are the small (1/8"???) lines that t into each carb, near the carb throat, behind the air box? They appear to be fuel lines that go into the accelerator pumps??

Thanks in advance!!!

[okoboji]

Yes, the 98 XL1200 has the same engine as the GP1200 and the mod would be the same.

So does this mean that this application would be using the 95 main jet or the 105 main jet? I saw a previous post earlier in this discussion where you mentioned the '98 XL 1200 should use a 105 main jet. Please advise.

Thanks

[Cutlass]

98 XL1200 has the 65U, non-power valve engine just like the GP1200 and the SUV. And therefore it uses the same 105 main jet for this mod.

[okoboji]

98 XL1200 has the 65U, non-power valve engine just like the GP1200 and the SUV. And therefore it uses the same 105 main jet for this mod.

Thank you. I was also wondering if you knew what the pop off pressure should be on the carbs for the '98 XL 1200 as well as the '99 GP 1200?

I ask because I've been told by a tech a Riva over the phone that for the '98, it should be 85 psi. I have a really hard time believing that's the case because it sounds way too high so I wanted to ask here.

Thanks

[Cutlass]

Thank you. I was also wondering if you knew what the pop off pressure should be on the carbs for the '98 XL 1200 as well as the '99 GP 1200?

I ask because I've been told by a tech a Riva over the phone that for the '98, it should be 85 psi. I have a really hard time believing that's the case because it sounds way too high so I wanted to ask here.

Thanks

On a completely stock setup carb, yes they are very high. I thought it was 75, but if they say 85...I believe it.

[molsonreddog]

Starving for fuel

Hi guys I know this is an old thread but I just did this modification on in XLT 1200 drilling out and putting the 95 Main on the return line at the last carburetor. After three-quarter throttle now my ski completely falls flat. Seems as if could starving for fuel. I am running European specs on the Jets which are larger than US specs. Wouldn't think this should make a difference. Your thoughts? Thanks

[Jonesyfxr]

Did you install T handles for the highs and lows??